A liquid crystal display (LCD) includes a thin film transistor (hereinafter, referred to as TFT) array for controlling arrangement of a liquid crystal, a liquid crystal panel including a color filter for color implementation, and a backlight unit for irradiating light to the liquid crystal panel. A minimum unit for color implementation of the liquid crystal display is a pixel and the pixel includes red R, green G, and blue B subpixels. (In some cases, the pixel further includes yellow Y or white W subpixel.)
In general, the light generated in the backlight unit is white light including all wavelengths of the red, green, and blue lights. When the white light transmits the color filter of the liquid crystal panel, only the wavelength corresponding to the color of each color filter is transmitted and the wavelengths of the rest of two colors are absorbed. Accordingly, a known liquid crystal display uses the color filter, such that use efficiency of light is largely deteriorated.
FIG. 1 is a configuration diagram of a liquid crystal display in the related art.
Referring to FIG. 1, the liquid crystal display in the related art includes a backlight unit 10 and a liquid crystal panel 20 and the liquid crystal panel 20 includes a TFT array panel including a TFT (not shown) for controlling transmittance of light through the alignment control of a liquid crystal layer 207 and a pixel electrode 205 and red, green, and blue color filters 215a, 215b, and 215c for color implementation.
The TFT array panel includes a TFT active element (not shown), a pixel electrode 205 controlling the transmittance of light by the alignment control of the liquid crystal in areas of the red, green, and blue color filters 215a, 215b, and 215c, and a lower glass substrate 203. Red, green, and blue of subpixel areas are determined by a gate electrode line (not shown) and a data electrode line (not shown) of the TFT array panel.
A color filter layer 215 is a configuration of the color image implementation of the liquid crystal panel 20 and forms a substrate together with an upper glass substrate 211, a common electrode 209, and a black matrix 217 preventing a mixed color due to light leakage. A lower polarizer 201 polarizing light irradiated from the backlight unit 10 is disposed at the lower surface of the liquid crystal panel 20 and an upper polarizer 213 polarizing the light transmitting the color filter layer 215 is disposed at the upper surface of the liquid crystal panel 20. The color implementation of the liquid crystal display is performed by combining the red, green, and white light L0 inputted from the backlight unit 10 to the lower portion of the liquid crystal panel 20 includes all the wavelengths of red, green, blue lights and the transmittance of light is changed according to the arrangement direction of the controlled liquid crystal layer 207 in the subpixel corresponding to each color to control the color of each pixel.
Meanwhile, since the liquid crystal display is a device of displaying an image by controlling the transmittance of light, the backlight unit 10 for irradiating the white light L0 to the liquid crystal panel 20 is disposed at the bottom of the liquid crystal panel 20. The backlight unit 10 includes a light source (not shown) generating the light, a light guide plate 101 with a reflective plate at the bottom thereof, a diffuser sheet 103, and a prism sheet 105. The light generated from the light source is collected in the light guide plate 101 to pass through the diffuser sheet 103 and the prism sheet 105 which are an optical sheet and then, be irradiated to the liquid crystal panel 20 (L0).
Herein, while the white light generated from the light source of the backlight unit 10 is irradiated to the liquid crystal panel 20 to pass through an lower polarizer 201, a TFT array substrate, a liquid crystal layer, color filters 215a, 215b, and 215c, and an upper polarizer 213, and the like, the white light is almost absorbed or blocked by the black matrix 217. Accordingly, finally, a light amount emitted from the surface of the liquid crystal display is no more than 10% of the light amount of an initially inputted light source to have very low light efficiency and consume high power due to the low light efficiency. Particularly, since the light transmitted through the color filters 215a, 215b, and 215c is about 30% and 70% is absorbed and dissipated, the color filter is a component having the largest light loss in the liquid crystal display.
Recently, a demand for low power for high-quality, thin film, large-size, and energy reduction of the liquid crystal display is increasing and particularly, in order to implement a 3D image, when 3D glasses are used, since the luminance of the 3D image is lower than a 2D image by about a tenth, improvement in the light efficiency of the liquid crystal display is more urgently required.